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This is interesting...

Seoul_lasers said:
Well, I tried Jerry's method. It works for the 405nm, but again, the problem is the 3-5 seconds of dead time for the warmup on those 445nm lasers. Still averaging +300mW too low.
Click to expand...

I'd like to see your graphs of the OPHIR head readings and your LaserBee II same time readings....

Trevor said:
It's possible to write a software differentiator I suppose - it would get you closer, but isn't a perfect solution.

Trevor
Click to expand...

I tend to agree.. We've tried that in the past but we weren't happy with it...
There was too much jitter in the readings before the thermopile actually
detected the max power.


Jerry
 
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I think I better understand how the metering is measured now, thanks Jerry. But it doesn't really explain why S_L has such different readings even after using your method. 300mW is quite a bit. That's about 15%.
 
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That's why I would like to see the 2 graphs...
I'm not yet sure as to what is happening....:thinking:

Jerry
 
Going to try another test tomorrow. I am going to do it again and see if I get a different result. This will be using the same laser as well (405nm-olike).
 
Why not use my suggestion?

Meter the laser on your Laser Bee. Once it gets a stable reading (at 45 seconds or so), move the beam onto the Ophir sensor. It will get a reading instantly, and you can compare the two.
 
rhd said:
Why not use my suggestion?

Meter the laser on your Laser Bee. Once it gets a stable reading (at 45 seconds or so), move the beam onto the Ophir sensor. It will get a reading instantly, and you can compare the two.
Click to expand...

Sorry wasn't ignoring you.
Yes, I try that too. 2 graphs then
 
Ok well I tried another laser of known power. I know that Daguin's 12x kryton is
700mW as the 12x diode sees 500mA from the driver. It was set and measured at ~700mW. It is quite stable.

2 files Ophir and the laserbee.
I started my laserbee and turned it on after 10 seconds... so 0=10sec and 60=70sec
measured mW = pk.665.8mW - av.660mW
Ophir = pk 702mW - av 680mW
It's over 30mW out on the laserbee and so is the average measurment. If you can call it that

Ophir shows clearly that there is a difference.

I took Jerry's advice here, and yes the result is FAR better.

Next graphs will be the 455nm from RHD.. Also there is a +300mW of difference between the 2 sensors.
Coming shortly.

Note:
700mW 12x build file is the laserbee file.
 

Attachments

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That's 5.4% apart. Probably within the compound margin of error between two LPMs right?
 
Seoul_lasers said:
Ok well I tried another laser of known power. I know that Daguin's 12x kryton is
700mW as the 12x diode sees 500mA from the driver. It was set and measured at ~700mW. It is quite stable.

2 files Ophir and the laserbee.
I started my laserbee and turned it on after 10 seconds... so 0=10sec and 60=70sec
measured mW = pk.665.8mW - av.660mW
Ophir = pk 702mW - av 680mW
It's over 30mW out on the laserbee and so is the average measurment. If you can call it that

Ophir shows clearly that there is a difference.

I took Jerry's advice here, and yes the result is FAR better.

Next graphs will be the 455nm from RHD.. Also there is a +300mW of difference between the 2 sensors.
Coming shortly.

Note:
700mW 12x build file is the laserbee file.
Click to expand...

Why did you not use the EagleEye Data Logging Graph when
using your LaserBee II...:thinking:
You can easily save any log file as an Image file.

Where exactly did you get your OPHIR head from...
You can PM me if that source is sensitive..


Jerry
 
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Here's something that I don't understand about your data:

- The Daguin 12x is 702 vs 665, a difference of 5.3%
- You say the 445 is 300mW different, implying 2600 vs 2300, a difference of 11.6%

I can accept the fact that two LPMs would differ in readings by some set percentage. But I have trouble understanding why the offset would be inconsistent at different power ranges. That suggests to me that one of the sensors isn't linear. Or the data is wrong.

BTW - don't quote AVG powers here for the purpose of comparison. They're not really comparable numbers. Even if you do as Jerry suggested and turn on the LaserBee at the 45 second mark (or whatever the normal warm-up delay of the sensor is), you're still comparing different things. You'd be comparing figures based on the first X minutes on one hand, and figures based on the X minutes that occur subsequent to an offset of Y seconds on the other. It's just completely different data.

"AVG Power" is such a poorly understood (and incorrectly utilized) stat around these parts. You can't compare "averages" of time periods that are not specified and consistent.
 
Well, one of the sensors could be absorbing one wavelength better than the other.

Ophir rates their sensors spectrally flat to within a small tolerance, so we know a 5% swing will not be an issue of its absorptive properties.

Since Jerry claims his coating is spectrally flat, I expect he can furnish us with a graph and put the matter to rest. I'm sure he kept the graphs from when he tested it in a lab. :)

Trevor
 
rhd said:
Here's something that I don't understand about your data:

- The Daguin 12x is 702 vs 665, a difference of 5.3%
- You say the 445 is 300mW different, implying 2600 vs 2300, a difference of 11.6%

I can accept the fact that two LPMs would differ in readings by some set percentage. But I have trouble understanding why the offset would be inconsistent at different power ranges. That suggests to me that one of the sensors isn't linear. Or the data is wrong.

BTW - don't quote AVG powers here for the purpose of comparison. They're not really comparable numbers. Even if you do as Jerry suggested and turn on the LaserBee at the 45 second mark (or whatever the normal warm-up delay of the sensor is), you're still comparing different things. You'd be comparing figures based on the first X minutes on one hand, and figures based on the X minutes that occur subsequent to an offset of Y seconds on the other. It's just completely different data.

"AVG Power" is such a poorly understood (and incorrectly utilized) stat around these parts. You can't compare "averages" of time periods that are not specified and consistent.
Click to expand...

I agree... stating averages just confused the issues.. The longer a test
is run the less the ramp up slope will show a difference in that average.
Since the duty cycle of Lasers are so short ant average reading is
skewed depending on the response time of the sensors.

@ Trevor... I'm not in the shop right now. I'll look for those files when
I'm back in the shop..

I'll also compare a 405nm...445nm Laser and 808nm on a LaserBee II..
OPHIR head and our Newport LPM.

I'll get back here once I get all this done. Don't expect this tomorrow.
We are booked solid for a few days...

@ S_l.... give me the text on the 2nd splash screen of your LaserBee II
when you 1st turn it 'ON'...


Jerry
 
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lasersbee said:
I agree... stating averages just confused the issues.. The longer a test
is run the less the ramp up slope will show a difference in that average.
Since the duty cycle of Lasers are so short ant average reading is
skewed depending on the response time of the sensors.

@ Trevor... I'm not in the shop right now. I'll look for those files when
I'm back in the shop..

I'll also compare a 405nm...445nm Laser and 808nm on a LaserBee II..
OPHIR head and our Newport LPM.

I'll get back here once I get all this done. Don't expect this tomorrow.
We are booked solid for a few days...

@ S_l.... give me the text on the 2nd splash screen of your LaserBee II
when you 1st turn it 'ON'...


Jerry
Click to expand...

Jerry the text on the second splash screen is as follows: 849-0, so this isn't a calibration issue. Also, after about 20 seconds, using the 405nm laser, which is when peak readings start, the laserbee shows a more realistic value. it's still a bit low... but usable.
665.8mW pk on laserbee VS 703mW on the Ophir. The other measurement on your sensor called av shows 660mW .. .Ophir is 680mW (av)... I will refrain from calling these averages.
I don't know what to call them.

I have no idea why 445nm is showing such a larger gap other than the reason suggested earlier about the sensor coating being faulty. Just curious about what manufacturer it might be?
 
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rhd said:
Here's something that I don't understand about your data:

- The Daguin 12x is 702 vs 665, a difference of 5.3%
- You say the 445 is 300mW different, implying 2600 vs 2300, a difference of 11.6%

I can accept the fact that two LPMs would differ in readings by some set percentage. But I have trouble understanding why the offset would be inconsistent at different power ranges. That suggests to me that one of the sensors isn't linear. Or the data is wrong.

BTW - don't quote AVG powers here for the purpose of comparison. They're not really comparable numbers. Even if you do as Jerry suggested and turn on the LaserBee at the 45 second mark (or whatever the normal warm-up delay of the sensor is), you're still comparing different things. You'd be comparing figures based on the first X minutes on one hand, and figures based on the X minutes that occur subsequent to an offset of Y seconds on the other. It's just completely different data.

"AVG Power" is such a poorly understood (and incorrectly utilized) stat around these parts. You can't compare "averages" of time periods that are not specified and consistent.
Click to expand...

Actually, not really. Our peak values for 445nm are "miles" apart on the Ophir and the Laserbee.. this is the lagtime on the sensor. The after warmup measurements are over 300mW of difference. getting low 2000's high 1900's for your build, which I know is higher. Forget the peak values... they can't be seen with the laserbee at all. 2654-2648mW see in the first few seconds on an Ophir and after warmup 2345-2355mW .. 1980-1900mW on a laserbee. Thats a hefty difference. Also every time I measure the readings seem lower. Also very odd.
The Ophir 20C shows a pretty consistant output in the mid 2350's for your build, which is
close to stated normal output after warmup.
Don't know what to say other than ???.
 
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Seoul_lasers said:
Actually, not really. Our peak values for 445nm are "miles" apart on the Ophir and the Laserbee.. this is the lagtime on the sensor. The after warmup measurements are over 300mW of difference. getting low 2000's high 1900's for your build, which I know is higher.
The Ophir 20C shows a pretty consistant output in the mid 2350's for your build, which is
close to stated normal output after warmup.
Don't know what to say other than ???.
Click to expand...

Here's what is needed. It's really simple / clear / unambiguous.

- Start metering the 445 on the LaserBee
- Once the graph gets a reading and levels out, immediately (while the laser is running, and you've got safety glasses on) move the beam to the Ophir sensor
- Take note of:
--- The reading on the LaserBee just before you moved it
--- The reading on the Ophir once you've moved the beam to its sensor

That eliminates all of the ambiguity in talking about "peak" or "average". The Ophir gets a reading fast enough that the laser really shouldn't have changed output power much in that ~2 to ~3 seconds that moving the beam should take you.

That's what needs to be done :) It's too tough to interpret otherwise, because everyone is called different figures different things. Even "peak" is getting some ambiguous treatment here, because "peak" isn't necessarily the same thing as "the point when a TEC based LPM attains a reading". So just stick to that methodology I've described above and relay the readings. That will be helpful for Jerry and Ophir (oh ya, they're regular readers here ;))
 
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rhd said:
Here's what is needed. It's really simple / clear / unambiguous.

- Start metering the 445 on the LaserBee
- Once the graph gets a reading and levels out, immediately (while the laser is running, and you've got safety glasses on) move the beam to the Ophir sensor
- Take note of:
--- The reading on the LaserBee just before you moved it
--- The reading on the Ophir once you've moved the beam to its sensor

That eliminates all of the ambiguity in talking about "peak" or "average". The Ophir gets a reading fast enough that the laser really shouldn't have changed output power much in that ~2 to ~3 seconds that moving the beam should take you.

That's what needs to be done :) It's too tough to interpret otherwise, because everyone is called different figures different things. Even "peak" is getting some ambiguous treatment here, because "peak" isn't necessarily the same thing as "the point when a TEC based LPM attains a reading". So just stick to that methodology I've described above and relay the readings. That will be helpful for Jerry and Ophir (oh ya, they're regular readers here ;))
Click to expand...

I have yet to try this with my own meters... when I have both of them on hand though, it will be interesting to compare notes.
 
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